1. Field of the Invention
The present disclosure generally relates to methods of reducing the effect of preheat period variation in shape memory alloy (SMA) actuators, and more particularly, to a system for and method of doing the same that utilizes the inherent characteristics of backlash and slack within the system.
2. Discussion of Prior Art
Shape memory alloy actuators vary in preheat period, i.e., the time it takes to heat the SMA actuator to just before activation, as a result of many inherent and external factors, including ambient temperature differences, the internal temperature of the actuator (i.e., degree of cooling), constituency differences from actuator to actuator, the cycle life/usage of the actuator, and the change in voltage (where activated on-demand) from circuit to circuit/application to application. Variation in preheat period presents concerns and challenges for systems operations as a whole, and more particularly, to software-based peripherals/algorithms (e.g., overload protection software) that rely upon preheat period as a trigger or for feedback. To compensate, actuators having large preheat period tolerances have been implemented; however, these tolerances present concerns of their own. Among other things, large tolerances reduce precision, and may result in the ineffectiveness of the system. In an overload protection algorithm, for example, imprecision may further result in the failure to timely abate an overload condition.